The above case demonstrates humeral metastases from a breast cancer primary. 

Histology

Macroscopic:
A right forequarter amputation including hand with five digits (140x90x55mm), forearm (240mm length, up to 85mm diameter), upper arm (300mm length and up to 150mm diameter) with scapula
(165x100x35mm). There is a soft tissue margin 160x130mm, inked black.

Within the soft tissue of the upper arm, there is a well demarcated rubbery to firm cream tumor with extensive areas of necrosis and cavitation, 140x110x105mm. There is invasion into, and in areas, complete obliteration of the humerus. Tumor is 4mm from the overlying skin, which shows mild dark brown discolouration. Tumor is 30mm from the soft tissue resection margin and more than 50mm from the bone resection margin.  The remaining skin and soft tissue are unremarkable.

Microscopic: 

Sections show the tumor show poorly differentiated carcinoma composed of sheets and interconnected nests of cells with large hyperchromatic markedly pleomorphic nuclei, moderate amounts of cytoplasm and numerous mitotic figures including abnormal forms, set within desmoplastic stroma.  There is moderate tumor necrosis.  Some areas appear vaguely squamoid.  Tumor involves fibrofatty tissue and skeletal muscle.  Sections of margins are clear of tumor.  The calcified sections are to follow.

Diagnosis:
Metastatic poorly differentiated carcinoma.