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Skin nonmelanocytic tumor

Adnexal tumors

Sweat gland derived (apocrine & eccrine glands)

Cutaneous mixed tumor / chondroid syringoma

Authors: Aadil Ahmed, M.D., Sara C. Shalin, M.D., Ph.D.

Resident / Fellow Advisory Board: Caroline I.M. Underwood, M.D.

Last author update: 23 June 2021

Last staff update: 1 November 2023

Copyright: 2002-2024, PathologyOutlines.com, Inc.

PubMed Search: Cutaneous mixed tumor or chondroid syringoma

Table of Contents

Cite this page: Ahmed A, Shalin SC. Cutaneous mixed tumor / chondroid syringoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/skintumornonmelanocyticchondroidsyringoma.html. Accessed December 19th, 2024.

Definition / general

Benign adnexal tumor of the skin composed of mesenchymal and sweat gland components
Morphologically identical to pleomorphic adenoma / benign mixed tumor of salivary gland
Most mixed tumors have both eccrine and apocrine components
Most are currently classified as apocrine type

Essential features

Slow growing, painless nodule on head and neck
Benign tumor of sweat glands with a myxoid stroma and cartilaginous metaplasia (Stedman: Medical Dictionary, 28th Edition, 2006)

Terminology

Other names include:
- Apocrine mixed tumor
- Eccrine mixed tumor
- Benign mixed tumor of skin
- Chondroid syringoma

ICD coding

ICD-10: D23.9 - other benign neoplasm of skin, unspecified

Epidemiology

Less than 0.1% of cutaneous tumors (Dermatol Surg 2003;29:179)
Middle aged men most commonly affected (J Am Acad Dermatol 2007;57:467)

Sites

Head and neck region involvement is common (nose most common site)
Extremities are less common (axilla most common site)
Rare cases of scrotum reported (J Int Med Res 1996;24:482, Int J Urol 2008;15:944)

Pathophysiology

Benign adnexal proliferation with a wide range of differentiation and metaplastic changes in its epithelial, myoepithelial and stromal components

Etiology

Unclear

Clinical features

Benign; rarely recurs
No distinctive clinical characteristics but may mimic pilomatricoma
Most often seen in middle aged men; mean age at presentation is 48 years
Most commonly in nose, followed by cheek and upper lip
Face / head and neck > extremities, trunk or back
Calcification / ossification may occur
Typically small (0.5 - 3 cm) and painless
No specific findings on dermoscopy
Rapid, ulcerative growth can be seen in malignant mixed tumor
Reference: Calonje: McKee's Pathology of the Skin, 5th Edition, 2019

Diagnosis

Biopsy required for diagnosis

Radiology description

Findings are not highly specific for chondroid syringoma over other dermal and soft tissue neoplasms (Australas Radiol 2001;45:240)
MRI can be helpful to determine the extent and depth of the lesion and relation to anatomic structures in large tumors
In the few cases studied, radiography of malignant chondroid syringoma tends to show higher signal intensity and enhancement (Australas Radiol 2001;45:240)

Prognostic factors

Benign, with rare recurrence
Malignant counterpart (malignant chondroid syringoma) rare with high rate of metastasis (60%) and death (25%) and should be ruled out on microscopic morphology (Pathology 1994;26:237)

Case reports

14 year old boy with eccrine spiradenoma with chondroid syringoma in Blaschkoid distribution (Indian J Dermatol Venereol Leprol 2009;75:600)
20 year old man with chondroid syringoma with extensive bone formation (J Clin Diagn Res 2014;8:FD15)
34 year old man with rapidly growing chondroid syringoma of external auditory canal (Case Rep Med 2011;2011:589680)
43 year old woman with chondroid syringoma of arm (Dermatol Online J 2006;12:14)
47 and 59 year old men whose tumors had prominent pilomatricomal component (J Cutan Pathol 2009;36:882, J Cutan Pathol 2012;39:718)
53 year old man with chondroid syringoma in the middle finger (Hand Surg Rehabil 2021;40:353)
55 year old man with 10 x 10 cm chondroid syringoma (Dermatol Surg 2003;29:977)
67 year old man with lipomatous mixed tumor with follicular differentiation (J Cutan Pathol 2006;33:389)
72 year old man with chondroid syringoma of the toe (Medicine (Baltimore) 2018;97:e9825)
Apocrine mixed tumors of the skin with architectural or cytologic atypia (Am J Surg Pathol 2007;31:1094)
Cutaneous apocrine mixed tumor with intravascular tumor deposits (Am J Dermatopathol 2011;33:775)

Treatment

Surgical excision is curative
Recurrence is rare
Electrodissection and CO2 laser have been used with slightly higher recurrence rate
Reference: Dermatology Advisor: Chondroid Syringoma (Mixed Tumor of the Skin) [Accessed 17 June 2021]

Clinical images

Images hosted on other servers:

Left supraorbital swelling

Single well defined nodule

Atrophy and scarring on surface

Gross description

Nodular, circumscribed, nonulcerated, with marked variation in size
Cut surfaces are tan-white, often with grossly apparent chondroid component
Slow growing, painless, firm, deep dermal to subcutaneous nodule

Gross images

Images hosted on other servers:

Well circumscribed, lobulated nodule

Microscopic (histologic) description

Well circumscribed but unencapsulated, multilobulated mass (separated by fibrous septae) centered in deep dermis or subcutaneous fat, with a prominent chondroid or myxoid stroma enveloping benign bland appearing epithelial and myoepithelial cells that form secondary structures (glands, ducts, cysts, reticular lace-like networks, nests)
Biphasic, with both epithelial and stromal components
- Epithelial: elongated branching tubular structures with 2 cell layers
  - Outer layer is cuboidal or columnar; inner layer is columnar with eosinophilic cytoplasm
  - Decapitation type secretion, often squamous metaplasia and basal nuclei
  - Often has areas of apocrine, follicular and sebaceous differentiation
  - Presence of any follicular or sebaceous features rules out pure eccrine mixed tumor
  - Wide array of morphologies can be seen with all types of differentiation along the folliculosebaceous unit
  - Occasional cases have neoplastic tubules connecting directly to normal follicular infundibulum
  - Follicular differentiation is the most common type of change in the epithelium and may include:
    - Keratinous cysts with infundibular keratinization
    - Isthmic epithelium
    - Hair bulbs with papillary mesenchyme
    - Matrical differentiation with basaloid, transitional and ghost cells
    - Trichohyaline granules
    - Vellous hair shafts
    - Anagen differentiation
  - Sebaceous differentiation may include single cells or islands of mature sebocytes
  - Metaplastic epithelial changes include clear cell change, columnar change, cytoplasmic vacuolization (may be abortive luminal differentiation), hobnailing, mucinous, oxyphilic, squamous
  - Metaplastic myoepithelial changes include clear cell change, collagenous spherulosis, hyaline cells, plasmacytoid cells, spindled cells
- Stroma: chondroid, mucoid or focally fibrous / hyaline
  - Metaplastic stromal changes include adipocytic, chondroid and osseous metaplasia
  - Adipocytic metaplasia may be extensive; some adipocytes may have Lochkern nuclei with a single small vacuole indenting the nucleus that resemble lipoblasts
In contrast to eccrine mixed tumors, apocrine mixed tumors do not have clear cell change, cribriform areas, osseous metaplasia (prominent), physaliferous-like cells, pseudorosettes
No pleomorphism or necrosis, sparse mitoses
Benign tumors may have:
- Asymmetry
- Mild nuclear pleomorphism within the ductal component
- Multinucleated, bizarre, hyperchromatic cells
- Infiltrative or pushing borders
Features suggestive of malignant transformation include:
- Severe atypia
- Markedly increased cellularity
- Increased mitotic rate
- Destruction of surrounding tissue
- Tumor necrosis
Reference: Calonje: McKee's Pathology of the Skin, 5th Edition, 2019

Microscopic (histologic) images

Contributed by Angel Fernandez-Flores, M.D., Ph.D., Aravindhan Sriharan, M.D. and J. Mike Magill, Jr., M.D.

Mixed tumor histology

Islands of epithelial cells

Epithelial tubules and ducts

Epithelial ducts

Chondroid stroma

Prominent duct formation

Metaplastic change

Cytology description

Many epithelial cells with bland nuclei in a chondromyxoid background
Marked nuclear pleomorphism and prominent nucleoli may be used to identify malignant features on fine needle aspiration (Acta Cytol 1998;42:1155)
Findings for diagnosis of chondroid syringoma on fine needle aspiration (Acta Cytol 2010;54:183)
- Fibrillary chondromyxoid background
- Prominent cellular component of epithelial and myoepithelial cells
- Absence of atypia and tumor diathesis (however, histology still required for definitive exclusion of malignant features)

Cytology images

Images hosted on other servers:

Cellular smear

Cellular aspirates

Positive stains

Immunohistochemistry generally not required for diagnosis
Inner epithelial layer: keratin, EMA, CEA, GCDFP-15, actin, cytokeratin 15
Outer myoepithelial layer / stromal component: S100, SOX10, NSE, GFAP, SMA, calponin, p63
Variable SMA, GFAP
p53 positivity of varying intensity
PLAG1 nuclear expression in apocrine mixed tumors (Am J Dermatopathol 2020;42:251)

Negative stains

Desmin (usually) (J Clin Pathol 2007;60:145)
p16 negative, in contrast to strong nuclear positivity in malignant chondroid syringoma (CRCP 2015;2:28)

Molecular / cytogenetics description

Positive for gene rearrangement of PLAG1 in largest study to date but lacks the characteristic translocations of PLAG1 seen in pleomorphic adenoma of salivary gland (Genes Chromosomes Cancer 2012;51:140, Virchows Arch 2011;459:539)
Small subset with ESWR1 rearrangement (Mod Pathol 2011;24:1444)

Sample pathology report

Skin, nose, biopsy:
- Chondroid syringoma (benign cutaneous mixed tumor)
- Microscopic description: Histologic sections demonstrate a well circumscribed nodular dermal (subcutaneous) neoplasm. The tumor consists of cords and islands of banal epithelial cells set in a variably fibrous and chondromyxoid stroma, creating a biphasic appearance. Ductal structures are present, with inner epithelial and outer myoepithelial layers evident. Cystic (or other metaplastic) change is seen. There is minimal nuclear atypia and mitoses are not abundant.

Differential diagnosis

Cutaneous chondroma:
- Lacks the epithelial and myoepithelial elements
Malignant mixed tumor / malignant chondroid syringoma:
- Necrosis, infiltrative growth, marked pleomorphism and greater cellularity
Metastatic carcinoma:
- Can often be distinguished based on immunohistochemistry and cytologic features of malignancy
Parachordoma:
- Rare, no true ducts, actin negative, presence of physaliferous cells, arises adjacent to tendon and synovium in extremities
- Now often considered a variant of myoepithelioma
Collagenous spherulosis:
- More common in breast, lumina contain dense eosinophilic secretion, no biphasic appearance
Hidradenoma papilliferum:
- No chondroid matrix, not biphasic
Myopeithelioma / adenomyoepithelioma of the skin:
- More common on extremities, myoepithelial areas should predominate, lacks luminal epithelial cells
- Negative for cytokeratin and CEA
Other adnexal tumors with apocrine differentiation

Board review style question #1

Features that are most suggestive of malignant behavior in mixed tumor are

Asymmetry, osseous metaplasia and scattered pleomorphic cells
Cytoplasmic vacuolization and plasmacytoid cells
Increased cellularity and necrosis
Infiltrative borders and asymmetry
Infiltrative borders and bizzare, multinucleated cells

Board review style answer #1

C. Increased cellularity and necrosis. Benign tumors may exhibit asymmetry, infiltrative borders, mild atypia, metaplasia and multinucleated cells. Features that suggest malignant mixed tumor are prominent pleomorphism / atypia, necrosis, increased cellularity and mitoses with tissue destruction.

Comment Here

Reference: Chondroid syringoma

Board review style question #2

Most common molecular abnormality seen in chondroid syringoma is

EWSR1 amplification
EWSR1 rearrangement
HMGA2 fusion
PLAG1 deletion
PLAG1 rearrangement

Board review style answer #2

E. PLAG1 rearrangement. Although the characteristic PLAG1 or HMGA2 fusions seen in pleomorphic adenoma of salivary glands are not seen in chondroid syringoma, PLAG1 rearrangement has been detected in a subset of cutaneous mixed tumors. Nuclear immunohistochemical expression of PLAG1 is also seen. A subset of tumors show EWSR1 rearrangement.

Comment Here

Reference: Chondroid syringoma

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