Metastatic Skin Tumors

Christine J. Ko, MD

David Cassarino, MD, PhD

Key Facts

Clinical Issues

Melanoma
- Nodule, often pigmented, may be ulcerated, multiple or solitary
- Nodal metastases; most commonly in regional lymph nodes
- Blue nevus-like melanoma: Blue macule/papule, often near original site of primary melanoma
- Survival often < 3 years, but varies
SCC and BCC: Nonspecific nodule(s), often pink to red
Merkel cell carcinoma: Nodal &/or distant metastasis common
DFSP: Essentially only the fibrosarcomatous variant

Microscopic Pathology

Metastatic melanoma
- Nodal metastases: Micrometastasis better detected with use of stains, i.e., S100, MART-1/Melan-A, HMB-45, MITF
- Cutaneous metastases generally lack an epidermal component (only rare epidermotropism)
Blue nevus-like metastatic melanoma: Virtually identical to blue nevus; history may be the key clue to diagnosis

Top Differential Diagnoses

All metastatic skin tumors: Primary skin tumor (rather than metastasis to skin from primary focus elsewhere in skin)
Nodal metastasis of melanoma: Nodal nevus (typically p16[+], low proliferation rate with Ki-67)
Merkel cell carcinoma: Other metastatic small cell neuroendocrine tumors

This patient with a history of melanoma on the chest has an unusual presentation of metastatic melanoma, with numerous 1-3 mm black-red papules.

This metastatic melanoma shows a lack of epidermal involvement, and is composed of nests of atypical cells with melanin pigment in the dermis.

TERMINOLOGY

Definitions

CLINICAL ISSUES

Presentation

Melanoma
- Cutaneous metastases
  - Nodule or papule, often pigmented, may be ulcerated, multiple or solitary
  - Rarely the presenting sign of disease
  - Occasionally primary tumor site cannot be determined
- Nodal metastases
  - Most commonly in regional, draining lymph nodes
- Distant metastases
  - Any site, including bone, gastrointestinal tract, lung, brain
- Blue nevus-like melanoma
  - Blue macule/papule, often near original site of primary melanoma
Merkel cell carcinoma
- Spreads to lymph nodes in up to 50-75% of cases
- Distant metastasis in up to 30-50% of cases
  - Other sites of metastasis include liver, lungs, bone, brain
Squamous cell carcinoma (SCC)
- Nonspecific nodules, often pink to red
- Rarely zosteriform pattern
Basal cell carcinoma (BCC)
- Very rarely metastasizes to other sites (lymph nodes, bone, parotid, lungs, other internal organs)
Dermatofibrosarcoma protuberans (DFSP)
- Essentially only fibrosarcomatous cases
- Often history of multiple local recurrences
- Rarely metastasizes
  - Lung most common site; also lymph nodes, bone, soft tissue
Many other cutaneous malignancies may metastasize
- Adnexal carcinomas
  - Sebaceous carcinoma: Relatively high incidence of metastasis
  - Microcystic adnexal carcinoma (extremely rare, with history of multiple recurrences)
  - Apocrine and eccrine carcinomas
  - Aggressive digital papillary adenocarcinoma (typically to lungs)
- Sarcomas that involve dermis

Treatment

Jul 8, 2016 | Posted by drzezo in PATHOLOGY & LABORATORY MEDICINE | Comments Off

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