Cutaneous metastases with a zosteriform pattern revealing concomitant pulmonary adenocarcinoma

Dear Sir,

Cutaneous metastases from internal malignancies are uncommon, occurring in 0.6–10.4% of cancer patients. Their zosteriform presentation is exceedingly rare, often mimicking herpes zoster and delaying diagnosis.^[1,2] The lungs, breast, and gastrointestinal tract are the most frequent primary sources of cutaneous dissemination. Nodular lesions represent the most common clinical presentation, and adenocarcinoma is the predominant histological subtype, particularly in lung cancer.^[1-3]

We report a 62-year-old male, a former smoker with a 15-pack-year history, who presented with a 3-month history of dyspnea and cough. Thoracic computed tomography revealed a 6.1 cm right parenchymal lung mass with associated mediastinal lymphadenopathy, large right pleural and pericardial effusions, and multiple pulmonary nodules with a miliary or cannonball appearance, as well as a suspected hepatic lesion, which remained indeterminate on initial evaluation. No additional distant visceral metastases were confirmed on initial thoraco-abdominopelvic imaging. A bronchial biopsy established the diagnosis of pulmonary adenocarcinoma.

Concomitant with the initial cancer diagnosis, the patient also exhibited multiple erythematous to violaceous, firm, and fixed nodules distributed linearly along the right T3–T6 dermatomes, with several ulcerated areas [Figure 1A]. These lesions were initially misinterpreted as herpes zoster and empirically treated with antiviral therapy, without clinical improvement. Dermoscopy revealed a central erosion with crust, a linear vascular pattern, a reticular pigmented network, and an erythematous background [Figure 1B]. The persistence of the lesions, along with the presence of linear, irregular serpentine vessels in this atypical zosteriform eruption, raised suspicion of a malignant process and prompted skin biopsy.

Close

Figure 1: 62-year-old man with zosteriform cutaneous metastases revealing pulmonary adenocarcinoma. (A) Clinical image showing multiple firm erythematous to violaceous nodules arranged linearly along the right T3–T6 dermatomes, mimicking herpes zoster. (B) Dermoscopic image of a representative nodule showing central erosion with overlying crust, linear serpentine vascular structures, a faint hyperpigmented reticular network, and an erythematous background.

Export to PPT

Histopathological examination demonstrated a dense dermal infiltration by atypical cuboidal to columnar epithelial cells arranged in glandular and cribriform patterns, exhibiting hyperchromatic nuclei and eosinophilic cytoplasm [Figure 2]. The epidermis was uninvolved. Immunohistochemical analysis showed tumor cell positivity for cytokeratin 7 (CK7) but negativity for thyroid transcription factor 1 (TTF-1). Although the lack of TTF-1 expression decreases specificity, the overall clinicoradiological and histopathological correlation supported a pulmonary origin. No definite vascular invasion was identified. These findings established the diagnosis of zosteriform cutaneous metastases from lung adenocarcinoma, associated with intrapulmonary, pleural, and pericardial involvement.

Close

Figure 2: 62-year-old man with cutaneous metastasis from pulmonary adenocarcinoma. Hematoxylin and eosin–stained section (×40) demonstrating dense dermal infiltration by atypical gland-forming epithelial cells arranged in irregular tubular structures (arrows), consistent with metastatic adenocarcinoma. The overlying epidermis is spared.

Export to PPT

The patient was referred to the oncology department for further evaluation and therapeutic management. A platinum-based chemotherapy regimen (carboplatin–paclitaxel with bevacizumab) was proposed during a multidisciplinary tumor board discussion but had not yet been initiated at the time of reporting.

Cutaneous metastases from lung cancer typically affect the chest, abdomen, or scalp, correlating with regional lymphatic drainage.^[1,3] The zosteriform distribution, however, represents a rare clinical mimic of herpes zoster. Similar presentations have been reported in association with breast carcinoma, melanoma, and gastrointestinal malignancies. Several mechanisms have been proposed, including retrograde lymphatic spread along dermatomal channels, perineural dissemination, or vascular spread involving previously affected dermatomes.^[2] In our case, the dermatomal distribution and unilateral localization strongly suggested lymphatic extension rather than coincidental dissemination. Such presentations can easily lead to misdiagnosis, particularly in elderly patients or those with atypical eruptions.

Dermoscopy, though underutilized in metastatic lesions, may provide valuable early diagnostic clues. In the study by Chernoff et al., vascular structures were observed in all non-pigmented metastatic lesions, with serpentine (linear irregular) or arborizing vessels being the most frequent patterns.^[4] These findings parallel the vascular features observed in our patient, highlighting the potential diagnostic contribution of dermoscopy in such cases.

Histologically, metastatic pulmonary adenocarcinoma in the skin generally preserves the glandular morphology of the primary tumor. Immunohistochemistry plays a decisive role in confirming pulmonary origin, with the combined CK7+/TTF-1+ profile being both sensitive and specific for adenocarcinomas of lung origin.^[3] However, a minority of pulmonary adenocarcinomas may lack TTF-1 expression while retaining CK7 positivity, particularly in poorly differentiated or mucinous subtypes, which may complicate immunophenotypic interpretation.^[3]

The appearance of cutaneous metastases simultaneously with visceral involvement signifies advanced disease. Prognosis remains poor, with median survival ranging from 3 to 6 months after the appearance of skin lesions.^[1,3] Nevertheless, early identification of these lesions can assist in staging, prognostic assessment, and appropriate oncologic management.

This case emphasizes the importance of considering metastatic disease in the differential diagnosis of zosteriform eruptions, especially in patients with known or suspected internal malignancy, and underscores the complementary role of dermoscopy, as vascular patterns may serve as early clues to underlying malignancy and guide timely histological confirmation.