Case report: Non-small-cell lung carcinoma presenting as a foot swelling.

Sir,

Acrometastases are defined as malignant secondary lesions of the bones located in the hands and/or feet. Acrometastases are very rare and are generally late manifestations of occult cancer and associated with a poor prognosis. In literature, only few cases of acrometastases due to occult lung cancer have been reported.[1] We report a case of acrometastasis to the left foot from an occult lung cancer.

A 55-year-old female patient presented with complains of pain and swelling in the left foot of two-month duration. Magnetic Resonance Imaging (MRI) of the left foot showed erosion of the cortex of the second metatarsal with marrow edema and associated soft tissue abnormality noted just anterior to the eroded cortex [Figure 1]. Biopsy from the second metatarsal bone was suggestive of metastatic deposit and tumor cells were positive for cytokeratin 7 (CK-7), Epithelial membrane antigen (EMA), Thyroid transcription factor-1 (TTF-1), and NAPSIN, suggestive of Non-Small Cell Lung Cancer, Adenocarcinoma (NSCLC) [Figure 2].

Figure 1

MRI of left foot showed erosion of the cortex of the second metatarsal with marrow edema and associated soft tissue abnormality noted just anterior to the eroded cortex

Figure 2

(a) H & E section showing tumor cells arranged in nests and glandular pattern. Tumor cells were positive for, (b) CK-7, (c) TTF-1, and (d) NAPSIN

On careful history taking, she was a 15-pack-a-year smoker. The whole body positron emission tomography (PET) computed tomography (CT) showed a left lung lower lobe, hypermetabolic, soft tissue mass and subcarinal and left hilar lymphnodes [Figure 3a]. A hypermetabolic soft-tissue mass in the left base of the second metatarsal, with enlarged lymphnodes, was seen in the proximal left external iliac, left obturator, left inguinofemoral, and popliteal regions [Figure 3b]. The epidermal growth factor receptor (EGFR) mutation was not detected in the biopsy specimen.

Figure 3

(a) PET CT showed a hypermetabolic soft tissue mass seen in the left foot with destruction of the underlying base of the second metatarsal, (b) Left lung lower lobe showed a peripheral lobulated hypermetabolic soft tissue mass

The patient was started on external beam radiation therapy (EBRT) to the left foot, followed by systemic chemotherapy with Pemetrexed- and Cisplatin-based palliative chemotherapy. Post two courses of chemotherapy she had a dramatic response to the treatment with a decrease in pain in the left foot.

Bone metastasis is a common occurrence in patients with advanced carcinomas, particularly in those with lung, breast, and prostate cancer. However, metastases distal to the knee are very rare and metastases to the bones of the foot are even rarer. Metastases to bone develop in 30% of all patients with cancer, with only 0.007 to 0.3% having acrometastasis.[1] The most common sources of acrometastasis are colorectal, renal, and lung carcinomas (50%), with the bladder, uterus, and breast responsible for 25% of the metastases to the foot.[2] Acrometastases are rarely the initial presentation of metastatic carcinoma. In a series by Healey et al., they were seen as the initial manifestation of an occult malignancy in four (14%) of the 29 patients.[3]

Acrometastasis are often initially mistaken for more benign processes, such as infection, trauma, inflammatory arthritis, osteomyelitis or gout. Persistent symptoms, unresponsiveness to conservative therapy or prior history of malignancy should prompt the physician to consider metastases, when evaluating a patient.

Given the bleak prognosis of digital acrometastatic lung cancer, treatment is largely palliative. Amputation and chemotherapy have been used, but recent literature suggests that localized radiotherapy can successfully relieve the pain and return the function to the affected foot.[4] There may also be a targeted role for bone-remodeling and pharmacotherapies, such as, bisphosfonates or denosumab, which have demonstrated utility in treating other bony metastases.[5] Treatment is directed toward the relief of symptoms and restoration of functional capacity.