Merkel Cell Carcinoma of the Thumb Masquerading as Acrometastasis—a Case Report

Acrometastases, although infrequent, are well known in medical practice (Stomeo et al. Eur Rev Med Pharmacol Sci 2015;2284-0729). While it may be the most probable diagnosis in a person with multiple lung lesions and an exophytic mass on the thumb, all cancerous lesions of thumb are not acrometastases. Histopathological examination is essential to ascertain the diagnosis—metastatic or primary tumor. A gentleman presented with an enlarging mass over his left thumb. X-ray showed a diffuse lesion replacing major part of distal phalanx, extending beyond its dimensions. He was worked up for amputation of thumb. During routine investigations for surgical fitness, chest x-ray revealed solid areas in bilateral lung fields. CT scan showed a large mass in left lung and a mass in the gall bladder. Working diagnosis of acrometastasis to thumb from a lung primary was made. Final diagnosis was Merkel cell carcinoma (MCC) of thumb with metastases to lungs, in light of histopathological findings. A primary skin tumor maybe misdiagnosed as a metastatic lesion in the presence of multisystem involvement. A high degree of suspicion and open mindedness thus needs to be kept even for rare diagnoses like Merkel cell carcinoma and a biopsy at the earliest be used for confirmation.