Table 4 Metastatic mimics
| Metastatic mimic | Common site | Histology | Immunohistochemistry |
| Lung | Anywhere (especially chest wall and abdomen) | Adenocarcinoma: intracytoplasmic mucin, lymphovascular invasion | Adenocarcinoma |
| Squamous cell: focal keratinisation and necrosis | CK7+/CK20− | ||
| Small cell: neuroendocrine features | (+) TTF-1 | ||
| (+) CEA | |||
| Squamous cell carcinoma | |||
| (+) HMWCK | |||
| (+) CK5/6 | |||
| (+) p63 | |||
| Small cell carcinoma | |||
| CK7+/CK20− | |||
| (±) TTF-1 | |||
| (+) Synaptophysin | |||
| (+) Chromogranin | |||
| (+) CD56 | |||
| Melanocytic markers | |||
| (−) S-100 | |||
| (−) HMB-45 | |||
| (−) Mart1/Melan A | |||
| (−) MiTF | |||
| Breast | Chest wall | Ductal: glands and comedo necrosis | CK7+/CK20− |
| Scalp | Lobular: single-row files of tumour cells | ER+/PR+ | |
| (+) AR in apocrine lesions | |||
| (+) GCDFP | |||
| (+) CEA | |||
| (−) S-100 | |||
| (−) HMB-45 | |||
| (−) Mart1/MelanA | |||
| (−) MiTF | |||
| Renal | Anywhere (especially head and neck) | Abundant clear cytoplasm | CK7−/CK20− |
| Vascular stroma | (+) Vimentin | ||
| (+) CD10 | |||
| (+) EMA | |||
| (+) RCC antigen | |||
| (−) S-100 | |||
| (−) HMB-45 | |||
| (−) Mart1/MelanA | |||
| (−) MiTF | |||
| Prostate | Genital region, anterior thigh | Gland formation | CK7−/CK20− |
| Hyperchromatic pleomorphic nuclei | (+) PSA | ||
| (+) PAP | |||
| (−) S-100 | |||
| (−) HMB-45 | |||
| (−) Mart1/MelanA | |||
| (−) MiTF | |||
| Thyroid | Head and neck (especially scalp) | Looks similar to primary thyroid carcinoma | Papillary and follicular |
| Medullary carcinoma may be Congo red positive related to the amyloid deposits. | CK7+/CK20− | ||
| (+) TTF-1 | |||
| (+) Thyroglobulin | |||
| Medullary | |||
| (+) Synaptophysin | |||
| (+) Chromogranin | |||
| (+) CD56 | |||
| Melanocytic markers | |||
| (−) S-100 | |||
| (−) HMB-45 | |||
| (−) Mart1/MelanA | |||
| (−) MiTF |
-
AR, androgen receptor; CEA, carcinoembryonic antigen; CK, cytokeratin; EMA, epithelial membrane antigen; ER, oestrogen receptor; GCDFP, gross cystic disease fluid protein; PR, progesterone receptor; HMB, human melanoma black; HMWCK, high molecular weight cytokeratin; MiTF, microphthalmia transcription factor; PAP, peroxidase-antiperoxidase; PSA, prostate specific antigen; RCC, renal cell carcinoma; TTF-1, antithyroid transcription factor antibody.
