Metastatic tumors and simulators

Christine J. Ko

It is important to distinguish cutaneous metastases from primary adnexal tumors of the skin. Adenocarcinoma metastatic to the skin is commonly of breast or lung origin. Focal areas of glandular differentiation may be highlighted with a mucicarmine stain. Metastases are most often situated in the mid to deep dermis. Epidermotropic metastases form intraepidermal nests.

Pearl

Positivity with both cytokeratin 5/6 and p63 is suggestive of a primary cutaneous adnexal tumor over adenocarcinoma metastatic to the skin.

Breast carcinoma

Key features

• Poorly differentiated adenocarcinoma

• Various patterns: single cells infiltrating through collagen, cords, and tubules of atypical cells, collections of cells with glandular formation, clusters of cells in pools of mucin, dense sheets of atypical cells

• Occasionally, there is epidermotropism

• Gross cystic disease fluid protein (GCDFP)-15 positive, estrogen receptor+, and cytokeratin (CK) 7+

Fig 26.1 Breast carcinoma

Breast carcinoma is the most common cause of cutaneous metastatic disease in women. In general, metastases are seen on the chest wall, sometimes as a result of direct extension of the tumor. Various clinical and histologic presentations are possible. Distinct subtypes are discussed below.

Carcinoma en cuirasse

• Single files of hyperchromatic cells with nuclear molding (black box cars)

Fig 26.2 Carcinoma en cuirasse

A cuirasse is a suit of armor made of leather. Carcinoma en cuirasse presents with woody induration of the skin. The skin is infiltrated by single files of hyperchromatic nuclei with prominent nuclear molding. Dense collagen is laid down between the tumor cells. Because the dermis is sclerotic, the punch is rectangular rather than tapered.

Inflammatory carcinoma (carcinoma erysipeloides)

Key features

• Tumor cells within dilated lymphatic vessels

• Congested capillaries

Fig 26.3 Inflammatory carcinoma

Clinically, the lesions present with skin erythema that ranges from faint macular erythema to an erysipelas-like presentation. Inflammation is usually absent histologically, and the erythema is likely secondary to blood vessel congestion.