Dermoscopy and high‐frequency ultrasound provide diagnostic clues in a gastric adenocarcinoma with cutaneous metastasis as the initial presentation: A case report

1.

Dear Editor,

Cutaneous metastasis from internal malignancy is a rare occurrence and is often associated with a poor prognosis. It can either indicate an advanced stage of widely disseminated tumors or serve as an early sign of tumor recurrence. ¹ Breast cancer and melanoma are the most common primary tumors associated with cutaneous metastases. ² However, the incidence of cutaneous metastasis in gastric cancer cases is low, accounting for less than 5% of cases. ³ In this report, we describe the dermoscopic and ultrasonic manifestations of cutaneous metastases in a patient diagnosed with gastric adenocarcinoma.

A 50‐year‐old male presented with multiple flesh‐colored and erythematous skin nodules on his trunk and lower limbs, which had been present for the past 5 months. The patient initially noticed a single painless flesh‐colored papule on his abdomen, which gradually enlarged and became an inflamed nodule over time. Subsequently, similar skin nodules appeared on other sites. Physical examination revealed multiple firm and infiltrating flesh‐colored or erythematous nodules measuring 1–2 cm in size on the patient's scalp, abdomen, left chest, right waist, pubic mound, right lateral thigh, and back (Figure 1A, B). These nodules exhibited resistance upon palpation and were not easily compressed.

FIGURE 1.

(A and B) The patient presented with multiple flesh‐colored and erythematous skin nodules on his abdomen, left chest and right waist. (C and D) Dermoscopic examination revealed dilated linear irregular and branching vessels with a reticular distribution on a red background. (E and F) Ultrasonographic examination using 50 and 20 MHz probes demonstrated multiple longitudinal hypoechoic areas in the superficial dermis, connected to larger hypoechoic areas in the deep dermis. These areas exhibited an irregular shape, an ill‐defined border, and infiltration into the subcutaneous tissue.

Dermoscopic examination of the nodules revealed dilated linear irregular and branching vessels on a red background (Figure 1C, D). High‐frequency ultrasound (HFUS) examination, performed using 20 and 50 MHz probes, revealed a hypoechoic area in the deep dermis with an irregular shape and an ill‐defined border, extending longitudinally upwards (Figure 1E, F). A skin biopsy confirmed the presence of numerous atypical cells scattered throughout the dermis (Figure 2A, B). The atypical cells displayed pleomorphism and hyperchromatism.Immunohistochemistry revealed positive staining for CK and MPO, with a Ki‐67 index of 80% (Figure 2C‐E). However, negative staining was observed for CD3, CD20, CD30, CD43 and CD68. Collectively, the dermoscopic, ultrasonic, and histological findings strongly indicated cutaneous metastasis.

FIGURE 2.

(A) Histopathological examination revealed scattered infiltration of atypical cells among the collagen fibers in the dermis (HE, ×100). (B) The atypical cells were pleomorphic and hyperchromatic (HE, ×400). (C and D) Immunohistochemical staining showed positive expression of CK and MPO in the atypical cells (×400). (E) The Ki‐67 index was determined to be 80% (×400).

To localize the primary tumor, a whole‐body (Figure 3) fluorodeoxyglucose positron emission tomography/computed tomography scan was performed. The scan revealed thickening of the gastric wall in the cardia region with slightly increased metabolic activity (SUVmax 3.6). Increased metabolism was also observed in multiple subcutaneous nodules throughout the body, particularly in the abdomen and back (SUVmax 1.5), as well as in multiple lymph nodes (SUVmax 3.5). The patient disclosed a history of alcohol consumption and intermittent heartburn for more than 10 years, which had been neglected due to the patient's tolerance of the symptoms. Subsequent gastroscopy confirmed the presence of poorly differentiated adenocarcinoma in the gastric cardia. Based on these findings, a diagnosis of skin metastasis of gastric adenocarcinoma was established.

FIGURE 3.

A whole‐body fluorodeoxyglucose positron emission tomography/computed tomography scan revealed thickening of the gastric wall in the cardia region, accompanied by increased metabolic activity (SUVmax 3.6).

Cutaneous metastases pose a significant diagnostic challenge as they can often mimic other skin conditions such as cutaneous sarcoidosis, dermatofibromas, and epidermal cysts. This misdiagnosis can lead to delays in treatment. ⁴ However, incorporating dermoscopy and HFUS into the diagnostic process can be beneficial in distinguishing cutaneous metastases from other conditions.

In nonpigmented lesions of cutaneous metastases, the most common dermoscopic finding is the presence of vascular structures, particularly linear irregular and branching vessels. ⁴ These vascular structures within a cutaneous nodule should be regarded as an important clue for cutaneous metastasis. ⁵ However, it is worth noting that in the case of cutaneous metastases from gastric adenocarcinoma, the density of vessels tends to be lower and significant dilation may not occur, which could be a characteristic feature specific to this type of metastasis. On the other hand, cutaneous sarcoidosis can exhibit two distinctive dermoscopic structures: either focally distributed or diffuse structureless orange or yellowish‐orange areas and well‐focused linear or branching vessels. ⁷ Dermatofibromas are primarily characterized by a peripheral delicate pigment network, a central white scar‐like patch, white network, homogeneous pigmentation, and vascular structures. ⁸ The “pore” sign serves as a significant dermoscopic indicator of epidermal cysts. ⁹

The HFUS findings in this case are consistent with features typically observed in aggressive tumors, including an ill‐defined border and an irregular shape. ⁶ It is speculated that the presence of a deep hypoechoic structure could be attributed to the infiltration of atypical and inflammatory cells among the collagen fibers in the dermis. Ultrasound imaging is also valuable in differentiating these conditions. Cutaneous sarcoidosis typically appears as dermal or subcutaneous hypoechoic areas surrounded by peripheral hyperechoic tissue, along with increased vascularity. ¹⁰ Additionally, a cobblestone pattern in the subcutaneous tissue may also be observed. Dermatofibromas manifest as avascular dermal and subcutaneous lesions with ill‐defined and spiculated margins, accompanied by changes in echogenicity in the surrounding tissues. ¹¹ Intact epidermal cysts typically present as well‐defined round or oval anechoic or hypoechoic structures in the dermis or hypodermis, sometimes featuring an anechoic tract connecting to the skin surface. ¹²

Despite the often subtle initial presentation of cutaneous metastases, a high index of suspicion is necessary to avoid overlooking them. Incorporating dermoscopy and HFUS into the diagnostic process can provide crucial clues for identifying cutaneous metastases and their underlying primary tumors.

FUNDING INFORMATION

National High Level Hospital Clinical Research Funding, Grant Number: 2022‐PUMCH‐B‐092; CAMS Innovation Fund for Medical Sciences, Grant Number: 2022‐I2M‐C&T‐A‐007; National Natural Science Foundation of China, Grant Number: 82173449

CONFLICT OF INTEREST STATEMENT

The authors declare they have no conflict of interest.

DATA AVAILABILITY STATEMENT

Research data are not shared.