‘Lung-digit’ syndrome in a cat

A 10-year-old DSH cat presented for a single swollen digit on the left foreleg. A fine needle aspirate was taken (fig.1) and following the results, the digit was amputated and submitted for histopathology (figs. 2&3).

Fig 1. This is a fine needle aspirate specimen from the swollen digit (stained with modified Wrights-Giemsa) that reveals a cohesive cluster of pleomorphic neoplastic epithelial cells. These cells have a high N:C ratio and contain large nuclei (compare them to the size of the RBCs in the background) with prominent nucleoli.
Fig 2. An H&E section of the skin overlying the amputated digit. The dermis is extensively infiltrated by nests and glandular acini of neoplastic epithelial cells that similarly infiltrate the underlying third phalanx associated with osteolysis.
Fig 3. An H&E section of the neoplasm at higher magnification. This section is focused on a glandular structure that is lined by neoplastic pseudostratified columnar epithelium. Note that some of the columnar cells are ciliated (red arrow). The black arrows point to goblet cells which are characterised by intracytoplasmic basophilic mucinous material.

Final Diagnosis

Metastatic adenocarcinoma to the digit


Adenocarcinomas affecting the digit of cats are not common but can either be primary (e.g. apocrine or eccrine origin) or metastatic. The morphological features of the neoplasm in this case including the presence of ciliated pseudostratified columnar epithelium (consistent with respiratory origin) and goblet cells are typical of metastatic disease. Primary pulmonary carcinomas are the most common neoplasms that can be associated with metastasis to the digits in cats. In some cases, multiple digits may be simultaneously affected and this should raise the suspicion of metastatic disease. Metastasis to the digits often occurs prior to the onset of clinical signs of respiratory disease however radiographs should help confirm the presence of a pulmonary mass.