Primary cutaneous mucinous carcinoma
The average age at diagnosis is 60 years. PCMC typically presents as a slow-growing papule, plaque, or nodule that can be red, pink, gray, blue, or purple. The lesion may have telangiectasias and may develop ulceration or crusting. Lesions are usually smaller than 8 cm and are most common on the eyelid or brow, followed by the rest of the face, scalp, axillae, and trunk. Truncal lesions have been associated with the worst prognoses.
PCMC was initially thought to be most common in men, but recent data has found more cases in females than males. Epidemiologic studies have shown that younger patients have a worse prognosis. Most data suggests that PCMC is most common among White patients, but a recent study revealed a higher prevalence in Black patients.
Endocrine mucin-producing sweat gland carcinoma (EMPSGC) is believed to be a precursor lesion to PCMC, and 50% of patients with EMPSGC have a concomitant invasive lesion.
C44.99 – Other specified malignant neoplasm of skin, unspecified
72495009 – Mucinous adenocarcinoma
Differential Diagnosis & Pitfalls
- Benign adnexal tumors – These include apocrine tubular adenoma, dermal duct tumor, hidradenoma, and hidrocystoma (cystadenoma). These can be differentiated based on histopathology.
- Keratinocyte carcinomas
- Amelanotic melanoma
- Metastatic mucinous carcinoma – More common cutaneous neoplasm. The most common primary mucinous carcinoma to metastasize to the skin is colorectal. Although metastatic mucinous carcinoma may have histologic features that differ from PCMC, including larger neoplastic cell clusters, less mucin, and lack of fibrous septa, there is no histologic finding to definitively distinguish the two malignancies.