Table 4 Metastatic mimics
Metastatic mimicCommon siteHistologyImmunohistochemistry
LungAnywhere (especially chest wall and abdomen)Adenocarcinoma: intracytoplasmic mucin, lymphovascular invasionAdenocarcinoma
Squamous cell: focal keratinisation and necrosisCK7+/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
BreastChest wallDuctal: glands and comedo necrosisCK7+/CK20−
ScalpLobular: single-row files of tumour cellsER+/PR+
(+) AR in apocrine lesions
(+) GCDFP
(+) CEA
(−) S-100
(−) HMB-45
(−) Mart1/MelanA
(−) MiTF
RenalAnywhere (especially head and neck)Abundant clear cytoplasmCK7−/CK20−
Vascular stroma(+) Vimentin
(+) CD10
(+) EMA
(+) RCC antigen
(−) S-100
(−) HMB-45
(−) Mart1/MelanA
(−) MiTF
ProstateGenital region, anterior thighGland formationCK7−/CK20−
Hyperchromatic pleomorphic nuclei(+) PSA
(+) PAP
(−) S-100
(−) HMB-45
(−) Mart1/MelanA
(−) MiTF
ThyroidHead and neck (especially scalp)Looks similar to primary thyroid carcinomaPapillary 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.