Diagnosis

Diagnosis

Metastatic renal cell carcinoma

Gross Differential Diagnosis and Discussion

Differential diagnosis and discussion: The gross image demonstrates two well-circumscribed lesions within the femoral head and neck. Cut surfaces are yellow-tan with hemorrhage and necrosis. There is no soft tissue extension. Given the history of a prior renal malignancy and the presence of multiple lesions, the macroscopic differential diagnosis is limited. Metastatic carcinoma, multiple myeloma, and metastatic melanoma are the top entities on the gross differential diagnosis. Multiple myeloma is also characteristically multifocal with lytic lesions (although solitary plasmacytomas do occur). Metastatic melanoma enters the differential diagnosis even in the absence of a known history of melanoma. Melanoma typically metastasizes to the axial skeleton (especially the ribs and vertebral bodies) and not the long bones and the lesions may be heavily pigmented or amelanotic.

The most common tumor of bone is metastasis. The primary diagnostic consideration in older patients with skeletal lesions is metastatic carcinoma. Carcinomas of the breast, lung, prostate, thyroid, and kidney tend to have bony metastases. In cases of carcinoma of unknown primary site, the lung and kidney represent the most common primary sites. Metastatic carcinoma and melanoma are much more common than metastatic sarcomas in the adult population. In the pediatric population, sarcomas are more common and may be primary (i.e. osteosarcoma) or secondary (metastatic).

The gross pathology may or may not be helpful to distinguish a primary bone tumor from a metastatic lesion. The presence of multifocality (as seen in this example) suggests metastatic involvement, although solitary skeletal metastases are not rare. Multiple myeloma is commonly multifocal and is actually the most common malignancy to involve bone. Radiographically, metastatic carcinomas involving bone may be osteolytic, osteoblastic, or mixed. Osteolytic metastases are typically from carcinomas of the lung, kidney, thyroid, adrenal, gastrointestinal tract, and uterus. Osteoblastic metastases are typically from carcinomas of prostate or bladder. Mixed osteolytic/osteoblastic metastases may be seen in carcinomas from the breast, lung, ovary, testis, and cervix.

Carcinomas with skeletal metastases are high stage by definition and if solitary, may be resected; however, the ultimate goal with metastatic disease is for all intents and purposes a palliative one.

References

1. Deyrup AT. Skeletal metastasis. Surgical Pathology. 2012;5:287-300.

2. Marino S, Roodman GD. Multiple myeloma and bone: the fatal interaction. Cold Spring Harb Perspect Med. 2018;8:a031286.

Go Back