Dermal intralymphatic invasion (ILI) in basal cell carcinoma (BCC) is defined as the presence of tumor cells within dermal lymphatic vessels. It has been associated with an increased risk of recurrence and metastasis, especially in tumors with aggressive histological features, such as the basosquamous subtype.
An 82-year-old man presented with a large 5cm×7cm BCC on the left temple, which was surgically resected with 1cm margins. Histological examination revealed a poorly differentiated neoplasm of epidermal origin consistent with basosquamous BCC. In the dermis adjacent to the tumor, multiple very thin-walled spaces were observed containing clusters of tumor cells identical to those of the primary tumor. Immunohistochemical staining with podoplanin demonstrated that these spaces corresponded to lymphatic vessels invaded by tumor cells. Of note is the striking image of a cluster of cells in transit from the dermis into the interior of lymphatic vessels (Fig. 1). This patient developed intraparotid and cervical lymph node metastases a few months after surgery of the primary tumor.
ILI is a histological finding that should be reported in the pathology report, as it represents an important risk factor for the development of metastasis.
